If you are able to immediately enroll in College Algebra/Chem 1151, the sciences take 4 semesters to complete. I know at other schools
it can be done in 2, but GPC has pre-reqs for their pre-reqs. I have heard of people taking Microbiology their first semester of Nursing classes though. I wouldn't recommend it, but you could bring it down to 3 semesters that way. This is IN ADDITION to the 2 year Nursing program. As far as exempting out of the COMPASS, the testing center would be able to tell you that.
Most classes are offered at all sorts of varying days and times, even on Saturdays. Additionally, pretty much all classes are available online, but you will have to take labs on campus. I prefer taking science and math on campus, but if you are disciplined and can teach yourself a great deal, it can afford you a lot of flexibility.
I'm not 100% familiar with the application process, as I am not planning to apply to their Nursing program (just taking my pre-reqs there). I do know you can apply as soon as you complete A&P I and take the TEAS.